After a year and a half of a trade war between the world's two biggest economies that choked off exports and foreign investment for the region, this was supposed to be South-east Asia's year of recovery.
A month into 2020 and that prospect is in doubt.
By some estimates, spending last year by Chinese holidaymakers during Chinese New Year hit about US$150 billion (S$205 billion).
This year, with more than 40 million people under some degree of quarantine across 16 cities in China, much of that will not be spent in the region's vacation hot spots.
And as China returns to work today after an extended holiday, exporters may face increasing pressure to hold on to orders as the country counts the cost of a coronavirus pandemic already bigger than the severe acute respiratory syndrome (Sars) outbreak.
"For 2020, there was optimism," Indonesia's Finance Minister Sri Mulyani said last week. "But already in January, that has done a U-turn."
The economic impact of Sars back in 2003 was estimated at US$40 billion worldwide, with as much as half of that focused on South-east Asia.
But with the advent of budget flights from Chinese cities to holiday destinations such as Phuket, and the shift of low-cost manufacturing from the mainland to countries such as Vietnam and Thailand, the impact this time may be worse.
Big brands such as Swedish furniture firm Ikea and tech giant Apple - which have been moving some manufacturing out of China and into neighbouring countries like Vietnam - are shutting stores as part of protection measures.
For now, the closures have had little impact on inventories and supply chains because shoppers have been away for Chinese New Year.
Last Monday, Indonesia's Trade Minister Agus Suparmanto told reporters that exports were still running "according to procedures" and that the outbreak likely would not have an effect on Indonesia's exports to China. Last year, Indonesia's exports tallied nearly US$26 billion.
Even so, it is already harder for some regional economies to export to their larger neighbour. Vietnam will keep closed its two main border crossings of Lang Son and Lao Cai for another week.
Mr Maxfield Brown, formerly with business risk advisory firm Dezan Shira and now an independent consultant, said: "When it comes to shipping and manufacturing, the real test will come as the Lunar New Year comes to an end."
For now, though, the deepest cuts are being felt in tourism.
Last Wednesday, Thailand slashed its gross domestic product growth rate forecast by half a percentage point to 2.8 per cent, owing to falling exports and a sudden slowdown in overseas arrivals following China's ban on all group tours.
Daily international arrivals to Bangkok and tourist centres such as Chiang Mai and Phuket have plummeted. With flights connecting to 33 cities in China, Phuket has borne the brunt of the downturn.
Last Tuesday, arrivals collapsed more than 28 per cent compared with the same day a year earlier as carriers cancelled services, according to Tourism Authority of Thailand data. Official data breaking down arrivals by country will not be available until later this month.
But Mr Bill Barnet, managing director and founder of Phuket-based consultancy C9 Hotelworks, said hotel managers are reporting there are signs that independent non-mainland travellers are shying away from Thailand too, worried they will get sick. "Travel sentiment is poor," he added.
In Bali, Mr Budijanto Ardiansjah, deputy chairman of the Association of the Indonesian Tours and Travel Agencies, told reporters Chinese arrivals will halve this year amid travel restrictions and flight cancellations.
Chinese tourists spend 14 million rupiah (S$1,400) on average each visit. The Indonesian government had said it hopes to earn US$20 billion in foreign exchange from tourism.
But Jakarta may need to settle for less than that. Yesterday, the authorities said Indonesia will temporarily stop flights to and from China starting from Wednesday.